Hydraulic fluid



Patented Apr. 4, 1944 John M. Clark and Ralph E. Van Deventer,.De-

troit, Mich, assignors to Packard Motor Car Company, Detroit, Mich, acorporation of a Michigan No Drawing. Application August 3, 1940,

Serial No. 351,102

3 Claims.

This invention relates to compositions of matter and more especially tofluids which are adapted to be used in hydraulic the transmission ofpower.

Such fluids are often subjected to extreme temperature variations andmust be so constituted apparatus for that they retain a relativelyinvariable viscosity,

a homogeneous texture, and resist decomposition, solidification, andseparation of the ingredients throughout the temperature range to whichthey are exposed.

Particularly difiiculty has been encountered in maintaining a one-phasecomposition in hydraulic fluids which contain castor oil when the fluidsare subjected to wide temperature variations,

berare also added to the solution of the castor oil in necessaryquantities.

The viscosity and other characteristics of the final fluid can becontrolled by the relative proportions of the ingredients. Asatisfactory range of ingredients in accordance with the presentinvention includes to 50% castor oil, 2% to 50% propylene glycol, 10% to70% butanol or isobutanol,- and an amount of potassium hydroxide whichvaries directly with the amount of the castor oil. The compositions ofrepresentative I fluids are'illustrated in the following chart:

since the composition of the oil includes compounds which will separatefrom the remainder of the fluid when it is allowed to stand for aprolonged period at low temperatures,

Castor oil is a mixture of several glyceryl esters of fatty acids,chiefly ricinoleic acid, also palmitic, oleic, and stearic acids andsome free fatty acid. The melting points of the glycerine esters ofstearic and ricinolelc acid are considerably higher than those of theother esters and this property causes these esters to solidify andseparate from the other constituents causing an undesirable change inthe hydraulic fluid when it is subjected to low temperatures, which are,however, considerably above those at which the remaining constituentsare so affected.

One object of the present invention is to provide a hydraulic fluidcontaining castor oil which is not ailected by extreme temperaturevariations and especially will not exhibit any tendency to form aprecipitate at low temperatures.

A further object is the provision of a process for producing a hydraulicfluid which will remain ,clear at all temperatures, which processfacili- -tates the solution of the different ingredients,

materially decreasing the time and dimculty usually involved in formingsuch compositions.

(Hydraulic fluids oi the type with which this invention is concerned mayvary widely in composition. The castor oil is generally'dissolved inorganic solvents and diluents or mixtures of them presence of astrongalkali such as potassium, so-

dium, lithium, or calcium hydroxide, is necessary Propylene glycol (byvolume) 33 a5 30 12 1o 15 15 Isobutanol (by volume) 4O 50 -55 Potassiumhydroxide (oz. per gal. castor oil) .15 to .302.

It is obvious that in the foregoing chart other glycols such asethylene, nonaethylene, hexaethylene, and tetraethylene may besubstituted for the propylene glycol and alcohols such as butanol,propanol, andisopropanol may be substituted for the isobutanol.

Castor oil (by volume) 0 In accordance with the present invention, the

higher melting fats found, in the castor oil, and particularly the'tristearine and triricinolein, are prevented from precipitating out ofthe finished fluid at low temperatures, by converting the same,

during processing, into a form in which they will remain in solutionregardless of temperature variations. This is accomplished by heatingthe solution to cause the alcohol in the composition to combinechemically with the higher melting fats to form corresponding lowermelting esters. The

to the reaction and it should be noted that weaker alkalis-and organicamines, as triethanolamine,

methylamine,- and. propylamine, are inefiectual. The alkali which isadded is completely neutralized when the reaction is complete, havingbeendepleted by reaction with the free fatty acid.

The preferred method of .the invention involves introducing the properproportions of castor oil and glycol to a suitable heating tank, to-'such as methanol, propanol, isopropanol, butanol, isobutanol, acetone,ethylene, propylene glycols, I

and other glycols, and some ketones and hydrocarbons. Compounds whichimpart lubrication qualities such as deflocculated graphite and metalsoaps, and compounds which inhibit the corrosive eilect of the fluidsuch as toluidines, alkalis, soap, dior tri-ethanolamine, and glycolswhich re-- gether with the alkali, the amount of which is determined bythe amount of the castor oil used. The alkali is added in the form of analcoholic solution which is'made with a small portion of the alcoholwhich is to be incorporated in the fluid. This mixture is then heated at180 Ito 220 F. with constant agitation for 15 to 20 minutes, at the endof which time the alkali should be neutralized. This "point can bedetermined by any standard indicator'reacting in alkaline soduce thecorrosive eflect of the alcohols on rublution, such as phenol-phthalein.The heating moved from the heating tank and run through a line meshstrainer to remove foreign particles. It is then cooled and placedin'containers ready for use. 5 r

The following example illustrates the process Thirty-three gallons ofcastor oil, 12 gallons of propylene-glycol, and 25 ounces of XOR in 2gallons of isobutanol as introduced into a heating tank and heated withagitation to 200 F.'until-the solution is neutral to phanolphthalein.Fifty-five gallons of isobutanoi are then added and the agitationcontinued until the so lution is homogeneous. It is then strained,cooled, and placed in containers.

While we do not desire to be bound by any theory as to the exactreactions which occur, it is believed that the tristearine andtriricinolein of the castor oil are converted to lower-melting esters byreplacement of the glycerol radical with the isobutyl or other radicalof the alcohol used, or a partially esterifled product containing bothradicals is produced, the soap formed by the reaction of the alkali andthe castor oil serv-' ing as a catalyst in such conversion reaetion.

Various modifications and substitutions other than'those specificallydescribed and mentioned are contemplated and may be made withoutdeparting from or sacrificing any of the advantages 5 oi the presentinvention.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is: I

l. The method of making a hydraulic fluid comprising heating at fromabout 180' I". to about 220 F., a mixture oi castor oiland a glycol inthe proportions of from one to live parts castor 1 oil to one part 01'glycol, in the presence of a strong alkaline catalyst dissolved in aquantity of 5 a monohydric alcohol, and then adding more or saidmonohydric alcohol until the whole amount of said monohydric alcohol is-from about 10% to about 70% oi! all of the ingredients. 2. An hydraulicfluid consisting essentially o 20 the reaction product obtained by.heating castor oil, propylene glycol, and isobutyl alcohol in thepresence of an alkaline catalyst.

3. The method of making an hydraulic iiui which comprises heating to atemperature 01 5 from about 180 F. to about 220 F. a mixture oi v castoroil with a substantially less amount by' volume of propylene glycol andisobutanol. in the. presence 01' a strongly alkalineca'talyst. thelatter being introduced in solution in the isobutanol, sucontinuing thereaction until the alkali is neutralized. and thereafter adding.isobut'anol in amount sufllcient to bring the total quantity ofisobutanol introduced to not substantially less than the total oftheremaining ingredients:

JOHN M. CLARK. Y RALPH E. VAN DEVEN'I'ER.

